ASTM D2129 Test Method for Color of Clear Electrical Insulating Liquids (Platinum-Cobalt Scale)
7. Preparation of Color Standards
7.1 Platinum-Cobail Stock Solution - Dissolve 1.245 g of K2PtCI6 (containing 0.5 g of platinum) and 1.000 g of CoCl2·6H2O (containing about 0.25 g of cobalt) in water. Add 100 mL of HCI (sp gr 1.19) and dilute to 1 L with water. This solution has a color of 500.
NOTE 1 - The color standard slock solution (platinum-cobalt solution) can be purchased with a color of 500 from laboratory supply firms.
7.2 Platinum-Cobalt Standards - The unit of color is that color produced by I mg of platinum per litre. From the slock solution, prepare color standards, as given in Table I, by diluting the required volumes to 50 mL with water in the Nessler lubes. Cap the tubes and seal the caps with shellac or a waterproof cement.
8. Procedure
8.1 Introduce 50 mL of the test specimen into a Nessler lube, passing the sample through a filter if it has any visible test specimen turbidity. Cap the tube, place in the comparator, and compare with the standards.
8.2 If the recorded color of the test specimen is greater than 300, do not use the platinum-cobalt scale. Use Test Method D1500 to measure color.
